JuniorAkademie

In order to not be in the eddying regime, this time we are rotating our tank as slowly as possible.

Since we ran the Hadley cell experiment the other day, I’ve been obsessed with running it again, this time with the slowest rotation possible in order to visualize a different flow regime – one were the heat transport happens through an overturning circulation rather than through eddies.

Unfortunately the camera we had mounted above the tank only started up halfway through the experiment (no idea how that happened!), so today you’ll only get snippets of this experiment. But all the more reason for us to run it again soon!

This is an experiment that I have been wanting to do for a long time, but somehow it never worked out before. But last night Martin and I finally ran it!

We ran two experiments, one after the other.

In the first one, we took a tank full of freshwater, added dye droplets and switched on a hair dryer to force mixing through the wind stress. After about a minute, the tank was fully mixed.

In the second experiment, we created a salt stratification: salt water with approximately 35 psu, and freshwater. We then added the dye droplets. The droplets never penetrated into the salty layer but instead layered in at the interface between the two layers. We then added the wind stress.

After a minute, the surface layer was well mixed, but there was no mixing penetrating into the bottom layer. To fully mix the whole depth, the wind forcing ran for 86 minutes.

Watch a short movie below and a movie containing the full time lapse even further down!

“At sea” in quotes, because technically we were at the mouth of the Weser river… But still! (deutscher Text unten)

The really exciting thing working with the kids here at the JuniorAkademie is that they are really good at transferring things that we talk about theoretically to what they see in a tank experiment, and even to what they see on the “real ocean”.

The day before we went on the student cruise, we did the wave interference experiments described here and here. But then “at sea” they saw a situation similarly to the one I filmed and posted below and they got so excited to see the same phenomena for real. One kid said that before, he couldn’t see the waves for the wave (alluding to not being able to see the wood for the trees), but that it was so cool to look at the water and see so much physics. Those are the moments we teach for, aren’t they? :-)

You might not have guessed it from reading about our waves meeting over a sandbank experiment, but we weren’t doing in purely for its entertainment value. Our goal was to see how waves interfere, because the theory of interfering waves seems to be counter-intuitive in some cases. A second experiment we have been doing on this topic is shown below. We create waves by dripping water drops on the water surface and film (and in some cases also watch) from below. Movie at the end of this post!